The forward advancing of a workpiece, specifically a bar or rod, through a lathe to permit sequential working operations to be performed has generally been accomplished using a push-type mechanism, commonly referred to as a bar pusher. The standard bar pusher typically comprises a sleevelike steel element formed substantially as a collet. This standard bar pusher is normally positioned on the rearward or backside of the lathe so as to engage the workpiece and push same forwardly. However, due to the size and mass of the bar being advanced, which bar may be as much as 12 feet in length, each stoppage of the pusher results in imposition of a substantial impact force on the lathe, and hence this significantly increases the wear and tear on the lathe.
To avoid the use of a spring steel collet as a pusher, another bar pusher has been developed which utilizes a steel-kept rubber insert captivated within a finger sleeve, which rubber insert is squeezed to deform same into gripping engagement with the bar so as to permit gripping engagement therewith and hence advancing of the bar. This known pusher, as illustrated by U.S. Pat. No. 2 426 200, is again positioned on the backside of the lathe collet. This pusher is also of undesirable axial length, and cannot be easily manually adjusted.
While bar pushers for advancing the bar or workpiece have been conventional and well known for many years, nevertheless the known bar pushers do cause excessive wear on the machine, and are relatively expensive in view of the requirement that they be positioned on the backside of the lathe collet. Due to the recognized disadvantages of the conventional bar pushers, one manufacturer, Advance Tool Systems, has developed a bar puller which mounts on the front side of the machine. In particular, this known bar puller mounts on the turret of a lathe, and hence can be advanced into engagement with the bar, and then retracted to permit advancing of the bar stock. This bar puller, however, requires that it be aligned with and movable into engagement with the free end of the bar to effect pulling thereof, and this hence makes the puller unusable in many environments, such as when the projecting bar is cut extremely close to the machine tool and has a very small projection, or when the bar must be moved into engagement with a center on the machine tailstock.
Applicant has also developed a bar puller which employs a sleeve, in this case an elastomeric sleeve, which moves coaxially into engagement with the free end of the bar to then effect pulling thereof. Applicant's earlier bar puller, as disclosed in copending application Ser. No. 519,630 file date Aug. 2, 1983, hence requires that it be coaxially moved into engagement with the free end of the bar in much the same manner as the bar puller manufactured by Advance Tool Systems, as described above.
Accordingly, the present invention relates to an improved bar puller which can be utilized to perform a desirable bar pulling operation in situations where prior known pullers cannot be successfully utilized. For example, in many instances a bar is cut off in close proximity to the lathe collet, so that only an extremely small length of bar projects from the machine collet. Known bar pullers generally cannot successfully engage the small projecting end of the bar so as to effect advancing thereof. In other situations the bar must be pulled outwardly of the headstock through a sufficient extent until the bar engages a center on the tailstock. Again, the known pullers which employ a sleeve which moves coaxially into engagement with the free end of the bar are hence wholly unsuitable for this type operation since they have no capability of being released from the bar after it is moved into engagement with the center of a tailstock. The improved bar puller of this invention is able to successfully pull a bar through a machine tool under use conditions similar to those outlined above, and hence this improved bar puller thus permits successful and efficient pulling of a bar under conditions which, when using known bar pullers, was either not possible or could be accomplished only with difficulty or only with consequent damage to the bar.
In the improved bar puller of this invention, the puller is provided with a body which mounts on the tool support so that the puller can be advanced radially toward the bar and also moved axially therealong to effect pulling. The body for the bar puller mounts thereon a pair of levers or rockers which project forwardly so as to effectively straddle the bar. These rockers mount rollers on the free ends thereof, the latter being provided with elastomeric gripping surfaces to effect gripping of the bar therebetween on approximately diametrically opposite sides. The support body for the puller preferably has an adjustable guide pin which is moved so as to abut the side of the bar, thereby providing a three-point support for the bar. Springs appropriately urge the rockers inwardly toward one another so that the rollers grippingly engage the bar therebetween. When so engaged, the tool support is moved axially of the machine to effect the desired pulling of the bar. The rollers are positioned so that they can engage only a short projecting end of the bar, and can also move the bar up against the center of a tailstock. When the pulling has been complete, the tool support is moved radially away from the bar, thereby retracting the rollers from their straddling engagement with the bar.
Other objects and purposes of the invention will be apparent to persons familiar with structures of this general type upon reading the following specification and inspecting the accompanying drawings.